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Old October 13th 08, 08:11 AM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

I am upgrading my very antiquated central heating. I am fitting a two
channel programmer, two 2 port zone valves for HW and CH, and an extra
pump for the HW which is gravity fed at present.

As I understand it, this constitutes a Honeywell S plan, and, except
for the extra HW pump, is shown at:

www.octaveblue.co.uk/c_heating/sp_hw.htm

and:

www.octaveblue.co.uk/c_heating/sp_ch.htm

but these diagrams only show a pump for CH which seems to be wired to
run all the time whether there is a call for heat for HW or a call for
heat for CH.

Is there any reason why I cannot wire the CH and HW pumps respectively
between the room thermostat and the CH zone valve, and the cylinder
thermostat and the HW zone valve? Or can anyone give me a link to a
wiring diagram for a fully pumped S plan system?

TIA

Keith

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Old October 13th 08, 08:41 AM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

On Oct 13, 7:11*am, Keefiedee wrote:

I think I've got it. The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than fed
from the switches in the motorised valves.

Will someone please confirm?

Keith
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Old October 13th 08, 01:58 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan



"Keefiedee" wrote in message
...
On Oct 13, 7:11 am, Keefiedee wrote:

I think I've got it. The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than fed
from the switches in the motorised valves.

Will someone please confirm?


On my system the end switches on all the valves connect to boiler on.
The boiler has a pump over run stat and connects to the pump.

You don't say what boiler you have or if you are changing it.
It may need an overrun stat if you remove the gravity loop.


Keith


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Old October 13th 08, 02:28 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

On Oct 13, 12:58*pm, "[email protected]"
wrote:
"Keefiedee" wrote in message

...

On Oct 13, 7:11 am, Keefiedee wrote:


I think I've got it. *The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than fed
from the switches in the motorised valves.


Will someone please confirm?


On my system the end switches on all the valves connect to boiler on.
The boiler has a pump over run stat and connects to the pump.

You don't say what boiler you have or if you are changing it.
It may need an overrun stat if you remove the gravity loop.





Keith- Hide quoted text -


- Show quoted text -


The boiler is oil - about 5 years old. Not sure what you mean by
overrun stat. Please clarify.

Keith
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Old October 13th 08, 10:29 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan



"Keefiedee" wrote in message
...


The boiler is oil - about 5 years old. Not sure what you mean by
overrun stat. Please clarify.


Runs for a period after the boiler has finished to allow the heat to be
removed from the boiler.
You don't need one with a gravity loop but the boiler may need one if you
remove the gravity loop.





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Old October 14th 08, 03:14 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

Keefiedee wrote:
On Oct 13, 7:11 am, Keefiedee wrote:

I think I've got it. The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than fed
from the switches in the motorised valves.

Will someone please confirm?

Keith



Why do you want two pumps?

You have two valves which are opened /closed by the room stat and tank stat.
If either valve is open, the boiler fires and the pump runs.


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Old October 14th 08, 06:58 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

On Oct 14, 2:14*pm, "PM" wrote:
Keefiedee wrote:
On Oct 13, 7:11 am, Keefiedee wrote:


I think I've got it. *The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than fed
from the switches in the motorised valves.


Will someone please confirm?


Keith


Why do you want two pumps?

You have two valves which are opened /closed by the room stat and tank stat.
If either valve is open, the boiler fires and the pump runs.


Because the HW and CH have separate pipework coming out of the boiler,
and the HW was only heated by gravity before I fitted the pump. I
know a pump isn't absolutely necessary, but I wanted a more efficient
system.
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Old October 15th 08, 05:25 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

Keefiedee wrote:
On Oct 14, 2:14 pm, "PM" wrote:
Keefiedee wrote:
On Oct 13, 7:11 am, Keefiedee wrote:


I think I've got it. The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than
fed from the switches in the motorised valves.


Will someone please confirm?


Keith


Why do you want two pumps?

You have two valves which are opened /closed by the room stat and
tank stat. If either valve is open, the boiler fires and the pump
runs.


Because the HW and CH have separate pipework coming out of the boiler,
and the HW was only heated by gravity before I fitted the pump. I
know a pump isn't absolutely necessary, but I wanted a more efficient
system.


That makes sense then!


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Old October 15th 08, 09:33 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

In an earlier contribution to this discussion,
Keefiedee wrote:

On Oct 14, 2:14 pm, "PM" wrote:
Keefiedee wrote:
On Oct 13, 7:11 am, Keefiedee wrote:


I think I've got it. The pumps don't go between the thermostats and
the motorised valves, but are fed from the thermostats rather than
fed from the switches in the motorised valves.


Will someone please confirm?


Keith


Why do you want two pumps?

You have two valves which are opened /closed by the room stat and
tank stat. If either valve is open, the boiler fires and the pump
runs.


Because the HW and CH have separate pipework coming out of the boiler,
and the HW was only heated by gravity before I fitted the pump. I
know a pump isn't absolutely necessary, but I wanted a more efficient
system.


So what you have *isn't* an S-Plan system - because that would only have
*one* pump.

With two pumps, you don't actually need any motorised valves. You simply
control each pump with its (room or cylinder) stat - and you then need some
relay logic to fire up the boiler when either (or both) pump is running.
[You may then find that you still get gravity circulation in the HW circuit
when only the CH is supposed to be on - in which case a simple check valve,
which requires pump pressure to open it, needs to be inserted into the HW
circuit.]
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!


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Old October 16th 08, 12:35 PM posted to uk.d-i-y
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Default Wiring diagram for fully pumped Honeywell S plan

So what you have *isn't* an S-Plan system - because that would only have
*one* pump.

With two pumps, you don't actually need any motorised valves. You simply
control each pump with its (room or cylinder) stat - and you then need some
relay logic to fire up the boiler when either (or both) pump is running.
[You may then find that you still get gravity circulation in the HW circuit
when only the CH is supposed to be on - in which case a simple check valve,
which requires pump pressure to open it, needs to be inserted into the HW
circuit.]
--
Cheers,
Roger
______

- Show quoted text -


I thought the difference between S plan and Y plan was that S plan
used 2 port motorised valves, and Y plan used 3 port valves?

Keith



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